Interior equipment of an automobile, such as an instrument panel, has a two-layer structure including a core and a foam layer made of a resin material such as polyurethane or polypropylene, and in general such interior equipment is manufactured in a die by injection molding.
A resin material in a molten state at a high temperature/a high pressure is charged into a cavity of the die made up of a stationary die and movable die, and then the movable die, for example, is opened to reduce a pressure in the cavity, thus foaming CO2 gas dissolved in the resin material to be in the form of bubbles. The amount and the speed of opening this movable die are adjusted appropriately so as to grow bubbles in an appropriate size, resulting in a foam layer (soft layer) with desired softness. Therefore, the thickness of the foam layer is determined by the expansion rate of the foam layer, and if this expansion rate or the thickness satisfies a predetermined value, then the foam layer will have predetermined softness.
Meanwhile, since interior equipment such as an instrument panel has a relatively complex shape and has a plurality of apertures, injection molding is conducted in the cavity defined by the stationary die and the movable die, followed by the movement of the movable die, for example, in a die clamping/die opening direction as a certain direction, so as to release the die from a molded article. That is, since opposing faces (or contacting faces) of both of the dies have a complex shape, their die clamping/die opening direction is limited to a certain direction, and even if the movable die is moved to other directions, such movement of the movable die will be inhibited because the die interferes with the molded article.
In the case where the foam layer is extended in a direction orthogonal to the die clamping/die opening direction, the movable die can move freely in accordance with the growth of the foam layer, so that the foam layer can grow up to an appropriate expansion ratio. On the other hand, if the foam layer has a shape including a face extended in another direction in addition to such a face extended in the direction orthogonal to the die clamping/die opening direction, the expansion ratio of the foam layer at the face extended in the other direction is not the same as the expansion ratio of the foam layer in the direction orthogonal to the die clamping/die opening direction, and therefore there is a high possibility that desired softness is not satisfied. Conventionally, allowing for such a problem, the foam layer extended in a direction different from the direction orthogonal to the die clamping/die opening direction is molded to be relatively hard. For instance, referring to FIG. 16 showing a conventional molding die, a molded article a made up of a core a1 having an aperture a11 and a foam layer a2 formed on a part of a surface of the core is molded in a cavity between a movable die b1 and a stationary die b2. Herein, the die clamping/die opening direction of the movable die b1 is X direction. The foam layer a2 is made up of a face a21 in the direction orthogonal to the die clamping/die opening direction and a face a22 rising obliquely from the face a21. When the foam layer a2 grows for foaming, the movable die b1 moves in X direction, and such movement enables the foam growth of the face a21 of the foam layer up to a predetermined expansion ratio in a foam growth direction Y1. On the contrary, since a cavity space corresponding to the foam growth of the face a22 of the foam layer cannot be secured, the foam growth in a foam growth direction Y2 is inhibited. As a result, the foam layer as a whole will be made up of a portion that grows up to a predetermined expansion ratio to have sufficient softness and a portion without sufficient softness because the portion cannot grow up to the predetermined expansion ratio.
Patent Document 1 discloses the invention relating to a die system capable of molding an article made up of a portion including a skin layer and a base layer and a portion including only a base layer using one die system. According to this die system, in a cavity defined by a core die (stationary die) and a cavity die (movable die), the base layer is firstly injection-molded. After the base layer is cured, a skin layer can be injection-molded on a predetermined surface of the base layer. Conventionally, after a base layer is molded using a different die system, the base layer is placed in a cavity of a die system for molding a skin layer and a skin layer is molded, and therefore there are problems that the manufacturing process of the molded article is long and the manufacturing is inefficient. The invention of Patent Document 1 is for solving such problems. Incidentally, the skin layer referred to in this invention corresponds to the above-described foam layer.
Patent Document 1: JP Patent Publication (Kokai) No. 08-85132 A (1996)